Google + Alexa: Cross-Assistant Apps

tl;dr - Let's develop an Action/Skill for Google and Alexa in one neat little package
Remember when the Echo was made available back in late 2014? It was invite only, then Prime only, then finally available for everyone the next summer. Only, most people didn't really seem to care. What does it even do? Why should I bother? Can't I just use my phone?
Fast forward to 2018, and it seems like everyone at least knows the Echo, and probably the Google Home. People know how to use them and why you'd have one. The question now has become "Which one should I get?" rather than "Why would I ever buy that?"
We've hit the point where people can reasonably expect skills to be on both the Amazon Echo and the Google Home. Both devices are in enough houses where it's worth the investment to create skills and actions for each platform. Luckily, this isn't nearly as difficult as it may seem.
We'll walk through the creation of both Alexa Skills and Actions on Google, look at the differences (there are a few, mostly names), look at what's the same, and see just how we can build a single application to serve both smart assistants. By the end of the session, we'll have a sample application running on both platforms from a single set of REST endpoints.